In recent years, light emitting diodes (LEDs) are widely used in daily lives because of many benefits and advantages such as power-saving efficacy. Until now, LEDs are widely used in many aspects such as display screens, household electrical appliances, vehicle electronic components, lighting device, and the like. Take a household lighting device using the LED as the light source for example. In comparison with the conventional incandescent lights and fluorescent lamps, LED has shorter warm-up time, quicker response speed, smaller size, longer life, higher power-saving efficacy, better shock resistance, lower contamination, higher reliability and higher productivity. With the maturity of the LED technology, LEDs will replace the conventional incandescent lights and fluorescent lamps.
As known, the current lighting device using the LED as the light source can produce light with a single color temperature. That is, the color temperature of the light source is mainly dependent on the LED of the lighting device. In addition, the color temperature of the LED is dependent on the fluorescent material contained in the LED. The fluorescent material to be added to the LED of the lighting device is determined before the LED is fabricated. Unless the LED of the lighting device is replaced with a new one, it is impossible to adjust the color temperature of the light outputted from the light source during the process of using the lighting device.
As known, it is inconvenient for the user to use the conventional lighting device. For example, if the light outputted from the LED has higher color temperature, the light feels harsh and cold to the eyes of the user. Since the color temperature of the light fails to be adjusted by the user, the light may discomfort or hurt the user's eyes. That is, the operations of the conventional lighting device are not user-friendly. Therefore, there is a need of providing an improved lighting device to obviate the drawbacks encountered from the prior art.